Stevens will be on the bench during the rebuilding of the Celtics, who, in a trade that will become official July 10, dealt franchise stars Paul Pierce and Kevin Garnett to the Brooklyn Nets for first-round draft picks and a plethora of players.

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Stevens is now the youngest coach in the NBA, and replaces Doc Rivers, whom the Celtics allowed out of his contract after nine seasons to coach Clippers in exchange for a first-round draft pick in 2015.

“Brad and I share a lot of the same values,” Celtics president Danny Ainge said in a statement released by the team. “Though he is young, I see Brad as a great leader who leads with impeccable character and a strong work ethic. His teams always play hard and execute on both ends of the court. Brad is a coach who has already enjoyed lots of success, and I look forward to working with him towards Banner 18.

Stevens will be introduced Friday at 11 a.m. at the Celtics Training Center at Healthpoint in Waltham.

Stevens, who was the youngest coach to reach the Final Four since Bob Knight in 1973, signed a 12-year contract extension with Butler in 2010 through 2021-22.